<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div{
            width: 1200px;
            margin: auto;
            background: #eee;
        }
        div li{
            width: 250px;
            height: 250px;
            background: red;
            float: left;
            margin: 10px;
        }
        .t1{
            width: 600px;
            height: 520px;
            float: right;
        }
        cf::after{
            content: '';
            display: block;
            clear: both;
        }
    </style>
</head>
<body>
    <div>
        <ul class="cf">
            <li></li>
            <li></li>
            <li class="t1"></li>
            <li></li>
            <li></li>
        </ul>
    </div>
    
</body>
</html>